An injector casing located in an opening in a cylinder head is usually provided in a fuel injection system. The injector casing serves to inject fuel into a combustion chamber located in the cylinder head. The injector casing has a valve stem portion and it should be possible to adjust the rounded projection of said valve stem portion very precisely in the combustion chamber. An upper section of the injector casing abuts the valve stem portion and has a larger cross-section than the valve stem portion. The upper section of the injector casing and the valve stem portion form a step, which rests on a continuous contact surface of the cylinder head located in the opening. A sealing element is placed between the injector casing and the cylinder head to seal the combustion chamber off from its surroundings. Generally the sealing element is configured in the form of a perforated disk with a rectangular cross-section perpendicular to the plane of the disk and it is positioned on the contact surface of the cylinder head. As the injector casing is being fixed in the cylinder head, the sealing element is pressed against the injector casing and against the cylinder head in such a way that substances in the combustion chamber cannot escape.
The injector casing must be pressed so firmly against the cylinder head that the sealing element is subject to plastic deformation, to accommodate any irregularities in the cylinder head and the injector casing. In the case of a sealing element in the form of a disk, the fixing force required to fix the injector casing in the cylinder head is so large that even the injector casing could be deformed.